Add minimum WebKit version to support table

[JohnRiv]

Similar to #379, a row for the minimum WebKit (or Safari) version for each year could be helpful

[JohnRiv]

In looking into doing this, do we want to record the Safari stable version numbers or the Safari Technology Preview release (or something else)?

I assume the Safari stable version numbers are most useful, but want to confirm before I proceed with gathering this information

[jpiesing]

In looking into doing this, do we want to record the Safari stable version numbers or the Safari Technology Preview release (or something else)?

I assume the Safari stable version numbers are most useful, but want to confirm before I proceed with gathering this information

I think the stable version is more relevant for what may be embedded in devices.